In conventional machine vision communication and control systems, a processor is connected to remote devices such as video cameras using a cable having numerous conductors. The cable includes multiple control lines for controlling operations of the camera. These operations can include focusing the camera, positioning the camera, and capturing a picture. The cable also includes data, synchronization and timing lines for transmitting video signals from the camera to the processor and additional lines for supplying power to the camera.
Different control systems have been used to control a plurality of cameras. One system uses a plurality of cameras, each requiring a separate controller and a separate communication cable. This system becomes cost prohibitive to implement as the number of remote cameras increase. In another system, one controller can communicate with more than one camera. This system, however, requires that all cameras be the same type and that only one camera acquire an image at a time. Both of these systems have difficulty achieving the speed and flexibility required to control a plurality of cameras simultaneously and are limited in the number of cameras which can be controlled. In a manufacturing setting where real-time control of a number of different devices is needed, such conventional systems are impractical and often undesirably expensive.
The distance which a controller and camera can be separated is limited by the cost and operating characteristics of the cable. A cable having numerous conductors is expensive to purchase, install and maintain. Further, most video cameras' output signals are in an analog format which is susceptible to noise and attenuation losses, distortion, cross talk and ringing over long transmission cable distances. The cameras, therefore, must be located in proximity to the controller, further reducing the flexibility of such systems. A typical maximum distance between a controller and a camera is approximately 100 feet.
A further disadvantage of conventional systems is poor interchangeability of different types of cameras. That is, because a camera is connected to the controller with a specific cable, changing a camera may require a cable of a different configuration. If the new camera uses a different communication format, further modifications to the controller are required. Finally, operating characteristics which vary among cameras such as horizontal and vertical timing cannot be easily adjusted remotely.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a fast, flexible and inexpensive communication and control system for video cameras and other remote devices.